The present invention relates to a silicon photonics device. More particularly, the present invention provides a compact Si-based MMI Mux/Demux with low loss and high extinction ratio for two wavelengths in O-band.
Over the last few decades, the use of broadband communication networks exploded. In the early days Internet, popular applications were limited to emails, bulletin board, and mostly informational and text-based web page surfing, and the amount of data transferred was usually relatively small. Today, Internet and mobile applications demand a huge amount of bandwidth for transferring photo, video, music, and other multimedia files. For example, a social network like Facebook processes more than 500 TB of data daily. With such high demands on data and data transfer, existing data communication systems need to be improved to address these needs.
Multiplexing has been employed to further expand the capacity of optical link. Wavelength division multiplexing (WDM) is one approach for transport optical signals with multiple wavelengths on a single fiber and wavelength multiplexer/demultiplexer (Mux/Demux) is a key device for handling such processes. Coarse wavelength division multiplexing (CWDM) is a form of multiplexing that uses a far broader photonic band spectrum with wider spacings between the wavelengths used than dense WDM (DWDM). For O-band of 1260-1360 nm, 4 CWDM channels of 20 nm channel spacing with center wavelengths at 1270 nm, 1290 nm, 1310 nm, and 1330 nm have widely adopted as a low-cost version of WDM for upstream transmission. The conventional Mux/Demux designs include Fiber Bragg Grating (FBG), Thin Film Filter (TFF), Array Waveguide Grating (AWG), waveguide-based delayed-line interferometer (DLI), and directional coupler (DC) while most have various drawbacks for O-band application especially for implementation of an optical transmission system based on highly integrated silicon photonics. FBG-based Mux/Demux requires additional optical circulator. TFF-based Mux/Demux has low loss but not easy to be integrated within a silicon photonics system. AWG-based Mux/Demux has high insertion loss and is usually temperature dependent so that the performance is poor. DLI-based Mux/Demux has an wavelength sensitive issue at O-band due to its involvement with multimode interference splitter and combiner. DC-based Mux has an issue of tight in processing tolerance and poor reproducibility.
Therefore, it is desired to develop improved compact Mux/Demux for splitting or combining two wavelengths in O-band.